X-ray Photoelectron Spectroscopy —— Application in Phase-switching Device Study Xinyuan Wang A

Outline Background Basic Principles XPS Instruments Data Analysis Application in Reference Paper

Background XPS, based on photoelectric effect, was first explained by Albert Einstein During the mid 1960 ’ s Dr. Siegbahn and his research group developed the XPS technique

Outline Background Basic Principles XPS Instruments Data Analysis Application in Reference Paper

Basic Principles X-rays o Irradiate the sample surface, hitting the core electrons (e - ) of the atoms o Penetrate the sample to a depth on the order of a micrometer o Useful emission electron signal is obtained only from a depth of around 10 to 100 Å on the surface o The X-Ray source produces photons with either certain energies, known as monoenergetic X-ray beam MgK  photon with an energy of eV AlK  photon with an energy of eV o

Basic Principles electron emission when transfer energy is greater than the electron’s binding energy Photon

Outline Background Basic Principles XPS Instruments Data Analysis Application in Reference Paper

Instrument The technique is widely used because it is very simple to use and the data is easily analyzed Commonly the system has three main modules o An X-ray source o An electron energy analyzer o A detection system

Instrument Ultra High Vacuum (UHV) environment o all the three modules are contained in a vacuum chamber o Signal of emitted electrons will decrease with residual gas molecules o Surface sensitivity of XPS The Sample o be stable in a vacuum chamber o sample size amenable to the instrument o surface of sample remains clean before and during analysis X-ray Sources o high energy anode materials with small line width o provide depth profiling capability

Outline Background Basic Principles XPS Instruments Data Analysis Application in Reference Paper

Data Analysis XPS Survey Spectrum o a wide scan over a region that provide strong peaks for all elements o identify elements present XPS peaks are sharp large C 1s resulting from the deposition of adventitious carbon from the atmosphere

Data Analysis Followed up by spectra around the elemental peaks of interest Depth Profiling o etch and analyze

Data Analysis Depth Profiling o concentration of different elements versus depth within 10nm Application in Reference paper

Data Analysis Chemical Shift o small changes in electron energy regarding to chemical environment of the emitting element o computer curve fitting of high-resolution XPS spectra

Data Analysis Similar process in reference paper

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